Conventionally, electronics, for example, used in ships, aircraft, motor vehicles, etc. are housed in the respective waterproof cases in order to prevent water from entering the their insides when they are used under conditions such that they are exposed to rainwater or moisture. The waterproof cases are each provided with a connector, through which the above-described electronics receive/transmit electric signals from/to the outside thereof.
Moreover, a waterproof case like that is often placed under a condition such that a relatively large change in temperature occurs. Therefore, when the changes from a high temperature to a low temperature and a low temperature to a high temperature are repeated, the waterproof case can be cracked and degraded in water-resistance.
In other words, a temperature change causes a pressure difference between an internal pressure of the waterproof case and the atmospheric pressure, thereby deforming the waterproof case. Such deformation is repeated, while the waterproof case is cracked.
Then, in order to solve the problem, it has been proposed a method of opening the inside of the waterproof case to the atmosphere thereby to keep the inside of the waterproof case at a pressure substantially equal to an atmospheric pressure (see JP-A-2000-228243).
More concretely, the waterproof case has a connector fixed on its side surface and the connector is connected to the circuit board inside the waterproof case. Also, the waterproof case has a communicating path formed therein to keep the inside of the waterproof case in communication with the inside of the connector. To the connector, an external connector is to be coupled. The external connector has a ventilating hole formed therein to open the connector inside to the atmosphere.
According to the configuration, the external connector is connected with the connector fixed on the waterproof case, whereby pressures of the insides of the connector and the waterproof case can be substantially conformed to the atmospheric pressure.
However, the above-described method, by which a through-hole for allowing a connection terminal to pass through the case is formed in the waterproof case, involves the formation of a communicating path other than the through-hole and as such, the manufacturing process of the case is made more complicated.
In addition, because the external connector may be exposed rainwater or moisture, it is required to ensure the water-resistance of the ventilating hole formed in the external connector. On this account, it is required to actually install a special water-repellent filter having both air permeability and water-resistance on the ventilating hole. As a result, the conventional ventilating method for a waterproof case not only involves a special member but also makes the manufacturing process more complicated and raises the costs.
Again, while a through-hole for allowing a connection terminal to pass through the case is formed in the waterproof case, it is necessary to form a communicating path in addition to the through-hole and as such, the manufacturing process of the case is made more complicated.
Moreover, a waterproof case like this has been formed from a high-strength metal traditionally, whereas attempts to form such waterproof case from a resin, which is wieldy and excellent cost wise, have been made in recent years. A waterproof case made from a resin is prone to be cracked owing to temperature changes. Therefore, it becomes increasingly important to substantially conform pressures of the insides of the connector and the waterproof case to the atmospheric pressure thereby to prevent the occurrence of a crack.